While 3DSes continue to fly off the shelves in Japan, Sony's newly-launched PS Vita saw its sales decline dramatically in its second week on shelves.

In all, the company sold just 72,479 units during the crucial Christmas week ending December 25, a historically low number for a console's second week on shelves and a nearly 78 percent drop from the units sold in its debut.

Supply constraints do not appear to be at issue here, as the system's life-to-date sales of around 397,338 units falls well below its initial shipment of 500,000 units.

It should be noted that the Vita is available in two models, a WiFi-only version (¥24,980/$320) and a more expensive model that adds 3G connectivity for a higher price tag (¥29,980/$385) and a monthly connectivity charge. Sony's shipment estimates do not break down the unit's numbers by SKU, nor does Media Create's sales data, so it is unknown if consumer demand for one model versus the other may be contributing to its overall sales.

At 72,479, the system was outsold by not only Nintendo's 3DS, but by the Vita's predecessor, PSP, as well as by Wii and PlayStation 3.

When 3DS launched in Japan in late February for around the same price as PS Vita's WiFi model, it sold 374,764 systems during its launch weekend. By comparison second-week sales dropped by less than 45 percent to 209,623.

Nintendo's portable, which has outsold all other consoles every week since its 40 percent price cut in August, pushed 482,200 units last week -- less than the 510,000 initially reported by Famitsu publisher Enterbrain but still a record high for the system.

That brings the number of 3DSes purchased since its launch to more than 4 million. Its sales have jumped in recent weeks thanks in part to a particularly strong software slate for the holiday that includes Super Mario 3D Land, Mario Kart 7, and Capcom's Monster Hunter 3G.

PSP was the second top-selling console last week despite having only one title that sold significantly last week (Bandai Namco Games' Magical Girl Lyrical Nanoha A's Portable). The PS Vita predecessor moved 101,121 units, up week-over-week from 64,468.

Below are the full sales rankings provided by Media Create and translated by NeoGAF for the week ending December 25, 2011 (The second chart lumps together sales of all models in a given line of hardware.).